Car propulsion scheme utilizing married pairs of propulsion units

ABSTRACT

This invention relates to a single or multivehicle propulsion control system having at least one married pair of propulsion units. The system is comprised of at least one married pair of propulsion units each having a plurality of selectable operating modes, one being a primary propulsion unit, while the other is a secondary propulsion unit. A propelling effort control device having a first and second state is operatively coupled to the secondary unit. A propulsion control logic unit is operatively coupled directly to the primary unit and indirectly to the secondary unit through the propelling effort control means. The propulsion units are controlled by the propulsion control logic unit and propelling effort control means to select a predetermined number of married pair operating modes, the selection of these modes closely approximating the propelling effort required to maintain a preselected vehicle speed relatively free from accelerating and decelerating effects.

United States Patent Donaldson [54] AR PROPULSION SCHEME [is] 3,656,037[4 1 Apr.11,l972

3,305,712 2/1967 Hoffman ..318/63 UTILIZING MARRIED PAIRS OF PROPULSIONUNITS Primary Examiner-Bemard A. Gilheany Assistant Examiner-ThomasLanger [72] Inventor: George W. Donaldson, McKeesport, Pa. Att0rney-H.Williamson, A. G. Williamson, Jr. and .l. B. [73] Assignee: WestinghouseAir Brake Company, Swiss- Sotak Vale} 57 ABSTRACT [22] filed: 1970 Thisinvention relates to a single or multivehicle propulsion [2]] A N 21,594control system having at least one married pair of propulsion units.

52 us. Cl ..3l8/59 T y t is p of at least, one married p of P PP 51 int.Cl. ..H02p 7/68 .umts each having 'p y of Selectable Operating [58]Field ofSearch ..3 1 8/5 1, 53, 60-64, modes, one e g a P i eropulsion twhile w r is 318/95 96, 5.9, 301404, 318 a secondarypropulsion unit. Apropelling effort control device having a first and second state isoperatively coupled to {56] kefernces Cited the secondary unit. Apropulsion control logic unit is operatively coupled directly to theprimary unit and ndirectly to the UNITED STATES PATENTS secondary lunitthrough the propelling Effort coiitrol means. The propu sion units arecontrol ed y t e propu sion control 805,188 11/1905 Dey ..318/303 logici and propelling effort control means to select a 3 312318 4/1967slaples 18/318 predetermined number of married pair operating modes, the2523J43 9/1950 f "318/53 selection of these modes closely approximatingthe propelling 2566 898 9/1951 Li ht fi 318 64 c en 6 effort required tomaintain a preselected vehicle speed rela- E tively free fromaccelerating and decelerating effects. ewis 2,933,667 4/1960 Purifdy..318/60 9 Claims, 8 Drawing Figures c -170 175a- "170a 17Za-- Kapuka'm81 07256 0126*.

Q? 197 50 I Wau'z Speed t:- 3 filfgorw'ed I w Tue/201226 691. 1199pepformmcp (la/we Train gamed .S'eecc'oa I Command Cozzr'o. 0366- I 95%1231222555035 l m I 99\ I01 I 191a II? I veocir g 1/217 Hcua .5 a JPflcpabc'arz VI pee f 1120 I Cbzzro PM Command 995465200 I 15 0990,IVQZLUOP/i Qmzparafiol? IIZe I 4 112/ 1i i J Patented April 11, 1972 5Sheets-Sheet 5 l lllllll CAR PROPULSION SCHEME UTILIZING MARRIED PAIRSOF PROPULSION UNITS My invention relates to a vehicular propulsioncontrol system.

More specifically, my invention relates to a single or multivehiclepropulsion control system having at least one married pair of propulsionunits. Where a single vehicle is involved the one or more married pairsof propulsion units would be on the single vehicle, while in the case ofa multi-vehicle operation, pairs of vehicles could have one of themarried pairs of propulsion units per vehicle. The propulsion controlsystem will cause the vehicle or vehicles to move along a predeterminedpath at a preselected speed relatively free from accelerating anddecelerating effects. The system is comprised of at least one marriedpair of propulsion units each having a plurality of selectable operatingmodes, one being a primary propulsion unit, while the other is asecondary propulsion unit. A propelling effort control device having afirst and a second state is operatively coupled to the secondarypropulsion unit. A propulsion control logic unit is operatively coupleddirectly to the primary propulsion unit and indirectly to the secondary,propulsion unit through the propelling efiort control device. Thepropulsion control logic unit selects a particular one of the operatingmodes for the primary and secondary propulsion units and directlyactuates that particular mode in the primary propulsion unit. Thesecondary propulsion unit is actuated into the particular operating modeonly when the propelling effort control device is in its second state.When the propelling effort control device is in its first state, thesecondary propulsion unit operates at a preselected reference mode. Thestate of the propelling effort control device is controlled by thepropulsion control logic unit in accordance with the propelling effortrequired to maintain the above-noted preselected vehicular speedrelatively free from accelerating and decelerating effects.

Mass transit in the years just past has been and will continue to belike a struggling giant shackled by the enormous capital investment thatgave the birthright to rapid transit nearly a half century ago.Something must be done to revitalize the quality of the ride experiencedby the passengers. Recent years have seen an exodus of passengers fromrapid transit forms of transportation to the now ubiquitous automobile.The poor quality of the ride from the passengers viewpoint has been afactor. The mass transit giant has been in urgent need of a transfusionto keep it alive. This transfusion is under way as new ideas andinnovations are pumped into the existing systems. The most commonapproach has been to propose entirely new schemes to enhance rapidtransit passenger comfort and thereby lure the masses back .to thetrain. These approaches invariably require that entire existing systemsbe abandoned. There is no question but the creation of sophisticatedsolid state speed control systems available today is to be lauded.

A major problem lies in passenger comfort while moving in transit fromone spot to another. Almost all recent development work in the field ofautomatic operation of rapid transit systems has generally requiredfairly precise (:tl to 2 mph.) speed regulation to permit short headwayoperation in combination with various safety assurance methods such asoverspeed protection. The majority of existing transit systems as wellas foreseeable transit systems use or will use contacts to switchresistance in series with the propulsion motor armature, shunts inparallel with the motor field, and various motor configurations toprovide propulsion control. This type of speed control which is commonlya cam control type has only a few, usually three or four, permanentoperating states. Precise speed regulation with these types ofpropulsion controls has severe limitations. There are only a few speedsat which the available tractive effort exactly balances the forcestending to retard the train and these speeds vary widely with grade.

Anyone who has traveled on the subways and intracity transit trains isfamiliar with the annoying acceleration and jerky ride that continuallyvexes the passengers aboard such trains. The invention to be describedhereafter solves many of the above-noted types of problems related topassenger comfort without the need to go to new transit propulsionsystems, all at a cost simplicity that elevates the invention to bedescribed into the realm of invention of the highest order.

Not only does the invention to be described cope with the problems ofexisting systems but also it provides a teaching that will greatlyenhance the operation of future systems which will call for discretevelocity operating speeds. These latter noted advantages will becomeevident as the description that follows progresses.

It is therefore an object of this invention to provide an improvedpropulsion system for existing transit systems without the need forreplacing the existing propulsion units.

Another object of this invention is to provide a smoother ride whilemaintaining a preselected speed by the use of various combinations ofpropulsion effort modes when one or more married pairs of propulsionunits are involved.

Yet another object of this invention is to provide an inexpensive,highly effective propulsion control system suitable for incorporation inexisting rapid transit systems which, because of its simplicity, is muchlower in cost than currently available propulsion control systems ofcomparable control capabilities.

Still another object of this invention is to provide a propulsioncontrol system which, because of its automated nature and basicsimplicity, greatly reduces the training time required of motormencurrently employed.

Another object ofthis invention is to provide a married pair propulsionunit control which will enhance all future propulsion unit controlwhenever each propulsion unit has preselected operating states or modes.

Another object of this invention is to provide married pair propulsionunit control, which married pair of propulsion units consists of aprimary and a secondary propulsion unit, the primary unit being actuatedinto a preselected operating mode and the secondary propulsion unitbeing turned on into the same preselected operating mode or being turnedoff in accordance with the propelling effort required for operation ofthe married pair of units in a preselected manner, the tuming on or offof the secondary propulsion unit accomplished through a propulsioneffort control means known as the X r-elay.

Another object of this invention is to provide married pair propulsionunit control, which is economical in cost, simple in structure, reliablein operation, durable in use, and efficient in service.

In the attainment of the foregoing objects, a vehicular propulsioncontrol system is provided which includes at least one married pair ofpropulsion units, one a primary propulsion unit, the other a secondarypropulsion unit, for causing vehicular movement along a predeterminedway at a preselected speed at a relatively constant velocity.

Basically, the system operates with a married pair of propulsion units,each having a plurality of selectable operating" modes. The propulsionunits in the preferred embodiment are" series-connected DC electricmotors. A propelling effort control relay having a plurality of contactsand a first and second state to control corresponding first and secondstates for each of the contacts is operatively coupled to the secondarypropulsion unit. A propulsion control logic unit is operatively coupleddirectly to the primary propulsion unit and indirectly to the secondarypropulsion unit through the propelling effort control relay and itsplurality of contacts.

The propulsion control logic unit selects a particular one of theplurality of operating modes for the primary and secondary motor anddirectly actuates that particular mode in the primary motor. Thesecondary motor is also actuated into that particular operating modeonly when the propelling effort control relay and its plurality ofcontacts are in their second state. The secondary motor operates at apredetermined reference operating mode which is the coast mode in thepreferred embodiment, when the propelling effort control relay, or Xrelay, and its contacts are in their first states.

The states of the propelling effort control relay and, in turn, itsplurality of contacts are controlled by the propulsion control logicunit in accordance with the propelling effort required to maintain thepreselected vehicle relatively speed free from accelerating anddecelerating effects.

The selection of the above-noted particular operating mode, and thecontrol of the states of the propelling effort control relay and itsplurality of contacts is a function of the combined effects ofacceleration and change in velocity.

The propulsion control logic unit could include acceleration anddeceleration responsive devices, but for purposes of setting forth themost basic approach there need only be a mechanism that is responsive tochange in velocity. Therefore, while velocity is the only parameterbeing measured, acceleration and deceleration inherently play a part inthe selection of any particular operating mode.

Other objects and advantages of the present invention will becomeapparent from the ensuing description of illustrative embodimentsthereof, in the course of which reference is had to the accompanyingdrawings in which:

FIG. 1 illustrates train propulsion curves typical of prior art singleor multi-train car operation.

FIG. 2 illustrates train or vehicularv performance curves which resultfrom the incorporation of the invention.

FIG. 2a illustrates a two-car arrangement, each car having five modes ofoperation, including coast.

FIG. 3 depicts a low speed portion of the train or vehicular performancecurves shown in FIG. 2, as well as velocity error which arises duringnormal operation.

FIG. 4 sets forth in block diagram form a preferred embodiment of theinvention.

FIGS. 5 and 50 represents a circuit diagram of the embodiment set forthin block diagram form in FIG. 4.

FIG. 6 portrays the required alignment for the viewing of FIGS. 5 and5a.

A description of the above embodiments will follow and then the novelfeatures of the invention will be presented in the appended claims.

Reference is now made to FIG. 1 which illustrates train propulsioncurves typical of prior art single or multi-train operation. Thesepropulsion curves are shown and described in the following publications:General Electric Instruction Manual GET2866, pages 1 to 43; The ElectricRailway" by Morris Buck, 1915, pages 84 to 126, specifically pages 111to 120; or Applications and Industry, July 1955, pages 147 to 152,specifically page 148. This graph shown in FIG. 1 is of importance tothe contribution to be described hereafter because it sets forth ingraphic detail the mode and manner in which prior art train propulsionsystems operated. As has been noted in the past, trains that operated inour rapid transit-environments were limited to a group of trainpropulsion curves which were generally defined as being an inching modeof operation or switching mode, a low speed operation, a medium speedoperation, and a high speed mode of operation.

Reference is now made specifically to FIG. 1 in which the curve 11 is aswitching or inching curve. This curve is a train motor propulsion curveand, as one can see, as the velocity increases, the tractive effort,which is measured on the ordinate axis, decreases. Velocity is shown onthe abscissa. Accordingly, the vehicle may operate on this switching orinching curve for a few seconds of its initial operation when the trainis starting to move from a zero velocity. It should be recognized thatwhenever trains of this type are employed, the operator of the train mayonly select a single discrete mode of operation. In other words, he maymove a master controller lever, not depicted, to a point which isindicative of low speed operation. When this occurs the inching orswitching mode of operation is automatically entered. In the alternativehe may select a medium, or two higher speed modes of operation. Wheneverthis is done, the entire train and all the propulsion units in each ofthe cars on the train operate in exactly the same mode. In other words,all train cars connected one after the other are placed in the switchingor inching mode as the vehicle starts its initial movement.

The second curve of significance here is the curve designated by thereference numeral 12 which is the low speed propulsion curve. To theright of it appears medium speed propulsion curve 13, as well as highspeed propulsion curve 14. As the legends indicate, when the inchingmode of operation, or switching mode as it may be termed, is beingaccomplished, the motors on the respective cars are connected in series,and as is well known in the art, all external resistance is placed inseries with the motors creating the speed tractive ef fortcurves shownin the figure. The curves that are depicted in FIG. 1 are typical of alltrain propulsion curves wherever there is a series motor employed andportions of the series resistance is shorted out in steps as the vehicleincreases in speed. Therefore, it will be appreciated that if a train iscommanded to enter into a low speed mode of operation, which is definedby the train propulsion curve 12, there will of necessity be certainmechanisms on the train which will be activated to control the deletionof resistances in series with the motors. As these resistances aredeleted, a family of train propulsion curves will be generated and thesecurves are shown as dotted lines in this figure on curves 18, 19 and 21.They may be termed incremental resistance curves and when the trainthrottle is positioned in a low speed mode of operation, the train willautomatically follow the path shown by the arrows which originate oncurve 111, the switching curve, and which arrows meet the incrementalresistance curve 18, and after a brief moment of performance along thisincremental resistance curve, determined by timing and/or a currentlimit relay, the next incremental resistance curve is approached as isindicated by the arrow which originates on the curve 18 and stops oncurve 19.

The deletion of resistances as a vehicle comes up to a speed ofapproximately six miles per hour is automatic, and when this speedreached the vehicles operate on the low speed propulsion curve 12. Thisautomatic deletion of resistance forms no part of the invention whichwill be described hereafter.

Once the vehicle has reached a speed, for example, of approximately sixmiles per hour, the train propulsion curve 12 is the curve which thevehicles propulsion units will then follow. This assumes that the mastercontroller, which is conventional, is in its proper position. This istrue whenever two or more vehicles are employed and in actuality willalso occur when a single vehicle is employed. This figure, however, isintended to convey the situation where at least two vehicles areemployed, having two individual propulsion units.

Returning now to the description of the performance of these vehicles,once the low speed propulsion curve 12 is reached, the arrow 15designates the direction which the train propulsion effort will follow.Accordingly, as speed increases, the vehicles tractive effort willdecrease until we reach, for example, a preselected speed of 15 milesper hour, shown as point 20 on the curve 12. At this point the operatorof the vehicle, not desiring to exceed 15 miles per hour, would move thethrottle handle to its off or coast position and the tractive effortwould drop to small negative tractive effort 'as indicated by point 24at the tip of the arrow 25. This small negative tractive effort ispresent because both trains are in a coasting mode of operation and areexperiencing slight dynamic brak: ing. The negative tractive effort ofdynamic braking is illustratedby the plurality of dynamic braking curves16 shown interconnected by solid vertical lines.

If, as has been proposed in this suggested illustration, the operator ofthe train desires not to exceed 15 miles per hour, he would wait aperiod of time, and the train, because of train resistance and smalldynamic braking effort, would begin to decelerate. The operator wouldthen have to make a decision as to when to return to his low speedpropulsion effort, and this might be determined by a velocity errorwhich he could note in a speedometer located in the cab of the train.Accordingly, should, as this figure illustrates, the speed drop to 1 1miles per hour, the operator of the train would then put the throttleinto its low speed mode of operation, and as the arrow 23 indicates, thetractive effort would return to a point on he curve 12.

With all the motors connected in series with all external resistanceremoved, the train would follow the train propulsion curve 12 back downagain to the point 20, and at that point the operator would again turnthe controller to its off position and the tractive effort would drop tothe coast mode of opera tion, that is, point 24 on one of the dynamicbraking curves 16. It can therefore be seen that the vehicle, in orderto maintain a constant speed of 15 miles per hour,would have to huntover a velocity error which may well be as much as 3 or 4 miles perhour, and in so doing there must be a repeated application of low speedpropulsion effort to bring the vehicle back to the desired 15 miles perhour velocity. It is this hunting action coupled with large changes intractive effort that provides the present discomfort experienced bypassengers when the vehicle is suddenly accelerated in order to bring itback up to the desired speed.

Not mentioned up to this point is the presence of the curve 17 which istermed a train resistance curve, and which train resistance curve hasbeen reduced to a formula referred to as the Davis formula. This formulaappears below:

where:

R Train resistance in lbs/ton n Number of axles V= Velocity in miles perhour A Front area in square feet W= Wt./axle in tons It can now beappreciated from a review of this formula that the train resistancecurve will be one in which the train resistance increases asthe velocityincreases. Of special importance to us here is that this trainresistance curve 17 passes through the area enclosed by the arrows 25and 23, propulsion curve 12, and dynamic braking curve 16. It should benoted that there is no train propulsion curve which passes through thepoint 26 which is the point where the train propulsion effort, if itcould match the train resistance, would exactly balance the load andtherefore allow the train to remain at a constant velocity. It is tothis problem that the invention to be described hereafter provides asolution in that by the incorporation of the invention there may beaccomplished an almost perfect balance of tractive etfort versus trainresistance, and thereby provide an extremely smooth ride at a relativelyconstant velocity.

Before leaving FIG. 1, mention should be made of the incrementalresistance curves 22 at the top of this figure, which incrementalresistance curves are automatically utilized as the train is brought upto its maximum speed, or its medium speed, in a manner which forms nopart of this invention, but is conventional in train propulsion systemsnow in use. To reiterate further, the curve 13, which is the mediumspeed curve, employs two motors in parallel with full field and twomotors in series, hereafter referred to as the series parallel mode. Thehigh speed propulsion curve 14employs two motors in series, two motorsin parallel, with series fields shunted, hereafter referred to as theseries parallel with shunted field mode. These propulsion curves, ofcourse, are typical of all series motors used in rapid transit today.

As noted earlier, FIG. 1 depicts a set of dynamic braking curves 16,which curves reflect the variable nature of dynamic braking. The dynamicbraking curve 16 enter the picture whenever the vehicles are in theircoast mode of operation. The fact that this curve is shown as a steppedcurve is due to the fact that the curves 16 are brought about by theautomatic addition or deletion of resistance to the motor windings. Theavailability of this stepped curve plays a significant role in theinvention to be described. Curve 16 has been shown as a stepped curve,but in reality is made up of a plurality of curves which have been shownconnected by vertical lines.

Reference is now made to FIG. 2. This figure illustrates train orvehicular performance curves which result from the incorporation of theinvention which is to be described more fully hereafter. FIG. 2a, whichis positioned to the right of FIG. 2, illustrates a two-car married pairarrangement, and while not shown it is to be understood that each carhas four propulsion modes of operation plus coast. The first of the fivemodes of operation which were illustrated in FIG. I is the coasting modewith both vehicles having their propulsion motors turned off, and thisof course produces the dynamic braking mentioned with reference toFIG. 1. The second mode is that of the switching or inching moderepresented in FIG. I, as well as FIG. 2 by the curve 1 1. The thirdmode is the low speed mode of operation represented by the curve 12 inboth FIG. 1 and FIG. 2. The fourth mode of operation is that of mediumspeed operation depicted by the curve 13 in FIG. 1 and FIG. 2, and, thefifth mode of operation, of course, speed which is represented by thecurve M in both FIG. 1 and FIG. 2.

At this point it should be kept in mind that today, transit systems aregenerally limited to one of these five modes of operation unless somesolid state motor speed control has been added to give them an infinitevariation of tractive effort over a given velocity change. But, as hasbeen noted, this is very expensive. Therefore, it is in this environmentthat applicants invention emerges because it has been recognized thatthere are in fact more performance curves to operate on then previouslyrecognized. This invention recognizes the fact that there are actuallymore train performance curves than there are train propulsion curves. Inthe past, because all propulsion motors were operated simultaneously inthe same modes on all most rapid vehicles of a train, the propulsioncurves which were shown in FIG. 1 also became the train performancecurves. But this invention recognizes the fact that aside from the trainpropulsion curves there are other train performance curves for marriedpairs of propulsion units which may and will appear when one of themarried pair of units is placed in one mode of operation and the otherturned on into the same modeof operation or turned off to coast inaccordance with the propelling effort required to maintain a constantvelocity. For example, a married-pair propulsion curve 31, not presentbefore, will appear when the car A of FIG. 2a is in its switching modeof operation and the car B is in its coasting mode of operation andtherefore applying a dynamic braking. We can see that the curve 31intersects the ordinate at approximately half the tractive effort shownby the switching curve 1]. Accordingly, we now have a train notavailable.

Similarly, the married-pair propulsion curve 32, not present before,will appear when the car A in FIG. 2a is in its series mode of operationand the car B is in its coasting mode of operation. We can see thatmarried-pair performance curve 32 initially represents a little lessthan half the tractive effort that would appear were both cars A and Bin series operation. The effect of dynamic braking in the train car Bcauses this curve 32 to be less than half the tractive effort than whenboth cars A and B are in the series mode of operation shown byperformance curve 12.

Similarly, the married-pair propulsion curve 34, not present before,will appear when the car A in FIG. 2a is in its seriesparallel mode ofoperation and car B is in its coasting mode of operation. Married-pairperformance curve 34 initially represents a little less than half thetractive effort (due to dynamic braking) that would appear were bothcars A and B in series-parallel operation.

Finally, the married-pair propulsion curve 38, not present before, willappear when the car A in FIG. 2a is in its seriesparallel with shuntedfield mode of operation and car B is in its coasting modeof operation.Married-pair performance curve 38 initially represents a little lessthan half the tractive effort that would appear were both cars A and Bin series-parallel with shunted field operation.

In view of the above discussion, it should now be readily apparent thatthere are actually available a greater number of performance curves thanheretofore recognized. In fact, we see in this particular embodiment atotal of eight performance curves plus a ninth coasting curve, notshown, which may be contrasted to five performance curves which wereavailable in the prior art arrangements. This means that if there isprois that of the high performance curve heretofore vided a means tojump from curve to curve, as shown in FIG. 2, the operator of such atrain would then be able to select a train performance curve which mostnearly approximated the tractive effort necessary to balance the trainresistance as shown by train resistance curve 17. This ability, ofcourse, will allow the maintenance of a relatively constant velocityfree from the inherent necessity to apply large amounts of tractiveeffort to bring the train back up to speed once the train has slowed tosome preselected velocity error. In fact, while this description hasbeen directed to the situation where there is one married pair of cars Aand B employed, it must be recognized that any number of married pairsmay be employed. At this point it should also be understood that, whilethe description up to this point has been of typical train cars havingfour propulsion motors, it is intended that the four propulsion motorsof each can be recognized basically as a propulsion unit, havingdifferent modes of operation.

The invention, of course,is not to be limited to the situation wherethere are only four propulsion motors employed, but is to be extended towherever there is a married pair of propulsion units or motors eachhaving more than one mode of operation. Therefore, all descriptivematerial hereafter will refer to propulsion motors as propulsion unitsand reference will be made to the different modes of operation ofpropulsion units rather than going into the detail of noting that thesepropulsion units have in this preferred embodiment a number of separatepropulsion motors within the propulsion motor units.

As may well be appreciated from the recent study of FIG. 2 and FIG. 2a,there is the presence of a multiple of married-pair train performancecurves that may be utilized in the operation of the train. For purposesof illustrating the invention, only the curves 31, ll, 32, and 12, shownin FIG. 2, will be treated as it is quite apparent that the inventionwhen explained in this environment will make obvious the addedstructures and circuits that would be necessary to cover the full rangeof available performance curves that are established by theincorporation of this invention. Accordingly, all discussion hereafterwill be directed to a system which is functioning between the curve 31and the curve 12 shown in FIG. 2.

With specific reference to FIG. 3, only the four above-noted curves havebeen illustrated along with dynamic braking curve 16. It is theenvironment of FIG. 3 where the married-pair train performance curveselection will take place and to which the descriptions of FIGS. 4, 5and 5a are tied for purposes of function operation.

Reference is now made specifically to FIG. 3 which illustrates themarried-pair train propulsion performance curves of a train having atleast one married-pair of propulsion units where each propulsion unit isconsidered to have only three modes of operation. The first is thecoasting mode which is represented by the stepped curve 16. The secondis depicted by the curve 11, which has been termed the switching curve,and the third mode of operation is the series operation married-pairtrain propulsion curve 12. Curves 31 and 32 are generated whenever car Aof FIG. 2a is in its switching mode and car B is in its coasting mode,and whenever car A of FIG. 2a is in its series mode and car B is in itscoasting mode, respectively. Superimposed on FIG. 3 are two additionalcurves not shown in FIG. 2. These curves are train resistance curves 17aand 17b. It will be noted that these curves appear in a relativelyparallel relationship to train resistance curve 17, and it is intendedthat these curves 17a and 17b represent different grades upon which thevehicles are operating. Accordingly, the train resistance curve movesupward towards 17a when an increasing grade is being approached, andthis train resistance curve would fall below curve 17 should the trainbe moving on a decreasing grade. Curve 1712 reflects the change inposition of the train resistance curve should the train approach adecreasing grade.

Before entering the discussion of the meaning of the curves of FIG. 3,it would be well to point out in advance the desired pattern of trainoperation that is to be explained by this series of curves. Here, forexample, if a selectable speed of 15 miles per hour were preselected,then it would be desirable for the train to start from zero or thestanding position and move at the maximum rate of acceleration possibleup until approximately 15 miles per hour. In order to preventovershooting the 15 mile per hour mark and reaching an overspeedcondition which would require the application of brakes, it has beenarbitrarily selected to reduce the tractive effort applied when thetrain is approximately 1 mile per hour below the set or desired speed of15 miles per hour. This hopefully would, in some situations, dependingupon grade, allow the train to come up to the set speed and thepropulsion effort would just balance the train resistance force and thedesired speed of 15 miles per hour would be maintained. But thisis arare situation and more than likely will be only infrequentlyencountered. Once the speed of 15 miles per hour is reached it is, ofcourse, important to automatically reduce the tractive effort to zeroand then start what will be described as a search of the existingmarried-pair train propulsion and performance curves for a curve whichnearly matches the train resistance at the given velocity. Once thismatching is accomplished, the train will then stay on thetrainperformance curve which most closely approximates the tractiveeffort necessary to maintain the speed of the vehicle close to the setspeed desired, in this case 15 miles per hour.

With this thought in mind, attention is directed to FIG. 3. When thetrain starts from zero, the tractive effort presented to the wheelsis-represented by the married-pair train. performance curve 11. Thevehicle would then, in its operation, move down along the curve 11,which is called the inching curve, to a point where arrow 27 interruptsthis curve. At this point, due to the inherent characteristics of acurrent limiting relay, typically in the system, there would be anautomatic subtraction of resistance from the propulsion units causingthe motors to move to a new incremental resistance curve 18, and thenafter a suitable change invelocity there would be another shift, asindicated by the arrow 28 to the incremental resistance curve 19, andagain on change in velocity, another shift to a higher curve 21, asindicated by the arrow 29.

Finally, in the last step, with the train operating along the curveindicated by the reference numeral 21, the train would then shift ontothe married-pair train performance curve 12 via the previously mentionedcurve 22.

v The train would then proceed down along the married-pair trainperformance curve 12 to a point 61, which point 61 can be seen to bedirectly above the 14 mile per hour indication shown on the abscissa. Atthat point the train would reduce its tractive effort by one half. Thiswould be accomplished by maintaining the first car of the married-pairin series operation and permitting the second car of the married-pair tobe in its .coast operation. This would cause the tractive effort at thispoint to drop, as shown by the arrow that starts at point 61, and godown to the curve 32 at point 61a. If the train resistance isrepresented by curve 17, the train operating point would move to theleft along curve 32 to point 60 where a balance point is reached. If thetrain resistance is less the train will continue to accelerate to thepoint 62 along the curve 32 at which point 62 the set speed having beenreached the tractive effort would drop to coast, i.e., minimum dynamicbrake, which is at point 64 on curve 16. It is apparent that with thetractive effort negative and the train resistance curve 17 positionedwhere it is, the load on the train and its inherent resistance willresult in the train decelerating.

As the train decelerates the curve selection process will take place. Itwill be seen that when the vehicle has reached its set speed of 15 milesper hour or zero velocity error, deceleration will begin occurring frompoint 64 until the train reaches a velocity error of minus one (1) mileper hour, or 1 mile per hour below set speed. This error is shown atpoint 65 on curve 16, at this velocity error the train will continue todecelerate due to the fact that the train resistance curve 17 is greaterthan the tractive effort provided by the propulsion effort afiorded bythe train operating on married-pair train performance curve 31. Thetrain propulsion control logic and propelling effort control means to bedescribed hereafter would then select married-pair train performancecurve 31 and point 66 thereon, whereupon the curve 31 would be followedback to point 67 which is representative of a minus two (-2) miles perhour velocity error. Here again, since the tractive effort isinsufficient to balance the train resistance as represented by curve 17,a continued deceleration would be experienced, and to cope with this,the propelling effort control means would actuate the propulsion unit ofcar B of FIG. 2a into its switch mode, while car A of FIG. 2a would beactuated into its switch mode by the propulsion control logic,married-pair train performance curve 11 being selected thereby, and asthe arrow indicates there would be a move from point 67 on curve 31 topoint 68 on curve 11. Again, since the tractive effort is insufficientto balance the train resistance as represented by curve 17, continueddeceleration would be experienced, and the propelling effort controlmeans would actuate the propulsion unit of car B of FIG. 2a into itscoast mode, while car A would be actuated into its series mode by thepropulsion control logic, married-pair performance curve 32 beingselected thereby, and as the arrow indicates there would be a move frompoint 69 on curve 11 to point 70 on curve 32 at a speed error of minusthree (-3) miles per hour. Here it will be noted that for the first timeat point 69 on curve 32 the tractive effort available is greater thanthe train resistance shown by curve 17. Accordingly, follow married-pairtrain performance curve 32 from point 70, as indicated by the arrow downto point 60 where the tractive effort will just balance the trainresistance. If the grade remains constant, the train will proceed at aconstant speed with just slightly more than 1 mile per hour velocityerror. It should be understood that while the set speed of 15 miles perhour is desirable, it is permissible to have errors on the order of /zto 4 miles per hour. These errors are quite acceptable as long as thetrain maintains the given error without significant variation invelocity.

There is a further feature that should be recognized at this point andthat is, as shown in the figure, there are superimposed on this graphtwo additional curves 55 and 56 which are in reality portions of curves.These curves 55 and 56 are meant to reflect the fact that when a trainis operating on the married-pair train performance curve 32, the secondcar of the married-pair combination will be coasting. With a carcoasting, the propulsion motors are operating in a dynamic brakingmanner as these motors are driven in generator fashion. At this point itshould be understood that when a car is in a coast operation, thedynamic braking that takes place varies depending upon the velocity andthe amount of resistance being switched automatically into the motorwinding arrangement to prevent overloading due to the generator action.Accordingly, the coasting car presents a varying dynamic force whichvaries as a function of train speed or as a result of the resistancebeing added or subtracted. It is this varying load effect of thecoasting car which is intended to be conveyed by the curves 55 and 56,which in effect are added to the train resistance at that givenvelocity. In other words, since the second car of the married-pair isdynamically braking at increasing or decreasing amounts, depending uponthe resistance being provided by the dynamic braking, the curve 17 willactually experience a fluctuation which will move in a range defined bythe curves 55 and 56, and by so doing it will cause the overall trainoperation to float back and forth across the train resistance curve 17and provide a dynamically fluctuating situation in which the tractiveeffort will continuously balance the train resistance load required tomaintain the train at any given speed with a minimum of acceleration anddeceleration.

Returning now to the system operation and a further study of the curvesof FIG. 3, while the discussion up to this point has been directed tothat situation where the train resistance curve 17 has been principallyconsidered, it should be recalled that curves 17a and 17b also showtrain resistance curves that reflect respectively the tractive effortnecessary when a train is on an increasing grade and a decreasing graderelative to curve 17.

In the functional description of a train coming up to a set speed of 15miles per hour with train resistance curve 17 in mind no mention wasmade of train resistance curve 17b. Should train resistance curve 17bhave been the curve under consideration, then the train would haveproceeded, functionally speaking that is, to hunt over the performanceloop defined by the points 62, 64, 65, 66, 67, 68, 69 and 70. It shouldbe noted that this is a smaller loop in area in comparison to the priorart loop shown in FIG. 1 and defined therein by point 20, line 25, point24, line 23, and curve 12. We return now to an expanded discussion ofFIG. 3, and particularly the occurrence of events should the traincontinue to decelerate from point 70. In the event that the trainresistance curve was even higher than curve 17a, namely, above the point70 on curve 32 and below the point 76 on curve 12, then when the trainwould be experiencing a continued deceleration from point 70 on curve32, the train would continue on married-pair train performance curve 32until it reached point 71. At point 71 there would be a velocity errorof minus four the train will begin to accelerate and the train will (-4)miles per hour and the propelling effort control means would actuate thepropulsion unit of car B of FIG. 2a into its series mode, whilepropulsion unit of car A in FIG. 2a would be maintained in its seriesmode by the propulsion control logic and, once again, married-pair trainperformance curve 12 would be selected at point 76. There would then besufficient tractive effort to overcome the trains resistance and therewould be a halt to deceleration. The train would then accelerate up tothe point 61 on curve 12, at which point the velocity error would beminus one (-1) mile per hour and, as noted earlier, the propulsioncontrol logic and propelling effort control means would selectmarried-pair train performance curve 32 and move from point 61 to point610. The train would then hunt over the loop defined by points 61, 61a,70, 71, and 76. The selection of the married-pair train performance ofFIG. 3 has been tailored to the circuits and apparatus described inFIGS. 4, 5 and 5a.

Reference is now made to FIG. 4 which illustrates a preferred embodimentof the invention in blockdiagram form. In this embodiment and the onedepicted in FIGS. 5 and 5a, only three modes of operation are consideredto be present in each of the married-pair of propulsion motors depictedin order that the curves set forth in FIG. 3, which show the capabilityof moving from married-pair performance curved to married-pairperformance curve, be employed to point out how the invention may bereadily involved in any multi-married-pair propulsion unit system.Specifically, FIG. 4 shows a car A and a car B having respectivelymarried propulsion units 81 and 82. The cars A and B travel along rails83 and 84 and receive power for the married-pair of propulsion unitsfrom third rail 86 via contact 87 and lead 88, which enters themarried-pair performance curve selection logic, and which in conjunctionwith propelling effort control means 91 provides performance curveselection to be described more fully hereafter.

There is shown leaving the married-pair performance curve selectionlogic four lines, three of which are train lines to which the propulsionunits 81 and 82 are either directly or indirectly electrically coupled.These three lines are the leads 170, 172, and 173. Propulsion unit 81 ofcar A is directly coupled to leads 170, 172, and 173 respectively vialeads a, 172a, and 173a and propulsion unit 82 of car 13 is indirectlycontrollably coupled to leads 170, 172 and 173 through propelling effortcontrol means 91 which is electrically coupled to propulsion unit 82 vialeads 170e, 1720 and 1730, respectively. A fourth line leavingmarried-pair performance selection logic 80, or lead 167, electricallycontrollingly coupled married-pair performance curve selection logic 80to propelling effort control means 91, which controls actuation ofparticular modes in propulsion unit 82 of car B.

There has been designated by the legend to the left of the dottedoutline portion the title Propulsion Control Logic",

also referred to by numeral 95. This propulsion control logic 95includes, immediately beneath the'propulsion unit 81 and shown inschematic form, a train speed tachometer 98 which has a drivingconnecting link, shown by dotted line 97, connected to a wheel 96 of carA. This rotating input 97, or driving link, will provide the train speedtachometer 98 with a rotary input that will be converted into a DCoutput which isa conventional output for this type of tachometer. The DCoutput will appear on lead 99, and have a direct relationship to thevelocity at which the train cars are traveling. Immediately beneath thetrain speed tachometer 98, and also a portion of the' propulsion controllogic 95, is a .train speed command control 100. It will be seen in thisblock 100 that there are a number of circular shaped buttons designatedby their markings l0, 15, 2O, 25, 30 and 35 miles per hour. Inoperation, this train speed command control unit 100 would be normallylocated in the lead vehicle, in this case car A, and the selected speedwould be made by pushing one of the buttons just noted which wouldproduce an output on lead 101, which in turn would be delivered to theactual speed versus command speed comparator 102, which has, as has beennoted, the lead 99 from the train speed tachometer 98, also entering it.It will be noted that selection of a set speed may also be accomplishedvia wayside cab signaling, but for purposes of illustration the presenttype of selection is incorporated.

The output signal which would appear from this conventional voltagecomparator would be a DC signal indicative of the velocity error as ameasure of the different in voltage that exists between the train speedcommand and actual speed at which the train is moving as has beenmeasured by the train speed tachometer 98. This DC signal will bedelivered over the electrical lead 111 to a velocity error detectionnetwork 110. This velocity error detection network 110 also receives asan input the output from train speed command control unit 100 over leads101 and 101a. The reception of the command speed on these leads willcontrol the number of propulsion unit operating modes to be employed inthe married-pair performance curve selection logic. It has been assumedfor purposes of illustration'of the invention that the command speed onleads 101 and 101a will be such that only the three previously statedmodes of propulsion unit operation will be employed. Accordingly, thevelocity error detection network 110 will, depending upon the velocityerror and required tractive or propelling effort to overcome that error,provide one or more outputs which are preferably electromagnetic outputsdesignated by arrows 112a through 112f which will in turn be deliveredto the married-pair performance curve selection logic 80, which, as wasnoted with reference to FIG. 3, in conjunction with propelling effortcontrol means 91, will cause, depending upon the velocity error present,a selection of a train performance curve that ultimately will balancethe train resistance with a tractive effort sufficient to maintain a constant velocity, or cycle between modes to maintain average speed.

Reference is now made to FIGS. 5 and 5a which will be studied inconjunction with FIG. 3, previously discussed. The alignment of theseFIGS. 5 and 5a is shown in FIG. 6. FIGS. 5 and 5a contain a circuitillustration of one embodiment of the invention which sets forth themanner in which the marriedpair train performance curves, noted earlier,may be selected as the train moves in a dynamic fashion up to apreselected speed. Shown in FIG. 5 is the train consisting of marriedcars A and B having married propulsion units 81 and 82 respectively. Thetrain is traveling on rails 83 and 84 and receiving power from a thirdrail 86, over contact 87 via lead 88 to the married-pair performancecurve selection logic 811 in FIG. 5a which has three output leads 170,172, and 173 directly coupled to propulsion unit 81 of car A over leads170a, 172a, and 173a, and indirectly coupled to propulsion unit 82 ofcar B through contacts a, b, and c of relay X and respectively, leads1700, 172s, and 1730. The contacts a, b, and c and relay X comprise thepropelling effort control means 91. Relay X is labeled the X relay.Output lead 167 of married-pair performance curve selection logiccontrols the energization and deenergization of the X relay which, inturn, controls the opening and closing of contacts a, b, and c all ofwhich are hereafter. Further in the case of propulsion unit 81, or theprimary propulsion unit of the married-pair of propulsion units 81 and82, whenever lines 172 and 173 are energized propulsion unit 81 will bein its series mode of operation. Whenever line 173 only is energizedpropulsion unit 81 will be in its switch mode of operation. Finally, ifneither line 170, 172, or 173 is energized then propulsion unit 81 willbe in its coast mode of operation.

In the case of propulsion unit 82 of car B, or the secondary propulsionunit of the married-pair of propulsion units 81 and 82, whenever line167-is energized, thereby energizing the X relay of propelling effortcontrol means 91 and closing contact a, b and c of the X relay, andsimultaneously lines 170, 172, and 173 are energized, propulsion unit 82will be in its series-parallel mode of operation. Once again, it will benoted that for purposes of illustration energization of line 170 will belocked out and the series-parallel mode will not be employed in thedescription of the preferred embodiment. Further in the case ofpropulsion unit 82, whenever line 167 is energized, thereby energizingthe X relay and closing its contact a, b, and c and lines 172 and 173are energized, propulsion unit 82 will be in its series mode ofoperation. Whenever lines 167 and 173 only are energized propulsion unit82 will be in its switch mode of operation. If neither line 170, 172, or173 has power, then propulsion unit 82 will be in its coast mode ofoperation. Finally, if line 167 is.not energized, the X relay will notbe energized and contacts a, b, and c of the X relay will be openedallowing no power to propulsion unit 82 and causing propulsion unit 82to be in its coast mode of operation.

Each of lines 167,170, 172, and 173 is energized in accordance with thecircuit operation of the married-pair performance curve selection logic80. It will be seen from FIGS. 5 and 5a that power is delivered to themarried-pair performance curve selection logic 80 from third rail 86over contact 87 and lead 88. Line 167 to the X" relay of propellingeffort control means 91 may be energized in one of two ways, i.e., thereare two paths of energization provided for the energization of line 167.The first is from the third rail 86 over contact 87 and lead 88, lead151, front contact Z2 of the relay Z included in the velocity errordetection network 110, to be described more fully hereafter, frontcontact B2 of relay B included in the velocity error detection network110, lead 156, front contact SP2 of the relay SP included in thevelocity error detection network 110, lead 169, front contact P2 of therelay P included in the velocity error detection network 110, lead 188,lead diode 202 to lead 167. The second path of energization for the line167 to the X relay of propelling effort control means 91 is from thethird rail 86 over contact 87 and lead 88, front contact Z2 of relay Z,front contact B2 of relay B, lead 154, back contact SP1 of relay SP,included in the velocity error detection network 110, lead 158, lead165, front contact S2 of relay S, included in the velocity errordetection network 110, lead 181, lead 184, to line 167.

Line 170, as previously noted, will never be energized in thisdescription due to the fact that back contact L02 of the lockout relayLO, included in the velocity error detection network, will remain openthrough the selection operation, i.e., relay will remain deenergized forreasons to be explained hereafter.

There are also two possible paths of energization for the line 172,keeping in mind that back contact L01 of the relay LO from contact Z2 ofrelay Z, front contact B2 of relay B, lead 156, front contact SP2 ofrelay SP, lead 169, front contact P2 of relay P, lead 188, diode 201,diode 204 to lead 172.

There are three possible paths of energization for the line 173. Thefirst is from third rail 86 over contact 87, lead 88, lead 151, frontcontact Z2 of relay 2, front contact B2 of relay B, lead 154, backcontact SP1 of relay SP, lead 158, lead 163, back contact S1 of relay S,lead 180, to line 173. The second path of energization for line 173 isfrom third rail 86 over contact 87, lead 88, lead 151, front contact Z2of relay Z, front contact B2 of relay B, lead 154, back contact SP1 ofrelay SP, lead 158, lead 165, front contact S2 of relay S, lead 181,diode 200, lead 182, to line 173. Finally, the third possible path ofenergization for the line 173 is from third rail 86 over contact 87,lead 88, lead 151, front contact Z2 of relay Z, front contact B2 ofrelay B, lead 156, front contact SP2 of relay SP, lead 160, lead 166,back contact P1 of relay P, lead 187, diode 204, diode 207, to line 173.

The coast mode for both cars A and B is achieved whenever relay Z ofvelocity error detection network 110 is energized thereby causing backcontact Z1 to close and-front contact Z2 to open, producing an opencircuit condition such that no power will reach either of the lines 167,170, 172 and 173.

Also shown protruding from the velocity error detection network 110 is alead 145 to a brake control circuit which brake control circuit will beactuated whenever the train, consisting of cars A and B, reaches anoverspeed condition, ar-

bitrarily selected to be /2 mile per hour velocity error. Theenergization path for lead 145 to the brake circuit extends from thirdrail 86 over contact 87, lead 88, lead 150, back contact Z1 of relay Z,back contact B1 of relay B, lead 145 to the brake control circuit. Itwill be noted that due to orientation of contacts B1 and B2 of relay Band contacts Z1 and Z2 of relay Z, brake and propulsion will never occursimultaneously.

A description of the velocity error detection network 110 and theenergization and/or deenergization of the relays LO, X, SP, P, S and Bwill now ensue-Shown also in FIG. 5 is the actual versus command speedcomparator 102 which receives as inputs the actual train speed on lead99 from train speed tachometer 98 and the preselected command speed onlead 101 from train speed command control 100. These speed indicationson the leads 99 and 101 enter conventional speed error amplifier A1through current limiting resistors R1 and R2 respectively. In thefeedback path of amplifier A1 there is shown a large capacitor C inparallel with a resistor R to prevent rapid changes in value andcompensate for noise effects on amplifier Al. Zener diodes D1 and D2limit amplifier voltage within a permissible range. A parallel outputfrom the train speed command control 100 on lead 101a conveys the setspeed to one input of a conventional amplifier A2 which along withfeedback resistor R8 and a second input from potentiometer PR7 comprisesa lock out comparator incor* porated to prevent the use ofseries-parallel operation modes for propulsion units 81 and 82 at verylow speeds. The output of comparator A2 is delivered to the baseelectrode of conventional N-P-N transistor Q1 through base currentlimiting resistor R9. The potentiometer PR7 is set at such a value so asnot to allow the comparator A2 to produce an output whenever the inputon lead 101a is representative of a set speed below a predetermined lockout speed, i.e., if the set speed is below the predetermined lock outspeed the output of amplifier A2 will be negative and the transistor 01will be in a nonconducting state thereby rendering transistorQ7, in thelock out relay circuit nonconducting and deenergizing lock out relay L0.The deenergization of lock out relay LO will cause tion of relay P. Uponenergization back contacts L01 and L02 located in the married-pairperformance curve selection logic to be opened. As was previously noted,the description of the preferred embodiment of the invention in FIGS. 5and 5a will be limited to a situation in which the set speed, 15 milesper hour being chosen, appearing on input lead 101a to amplifier A2 willbe one below a predetermined lock outspeed, arbitrarily chosen at 17miles per hour, and lock out relay LO will remain deenergized throughoutthe married-pair performance curve selection operation, i.e., theseries-parallel mode of operations for propulsion units 81 and 82 willnot be incorporated into the present description. 7

The output of the comparator amplifier A1 of the actual speed versuscommand-speed comparator 102 appears across the resistor R6. A portionof the voltage across resistor R6 is tapped by the velocity errordetection network as shown in FIG. 5 and appears on lead 111. Shownwithin the velocity error detection network 110 is a series ofcomparator circuits for receiving the output of comparator amplifier A2on lead 111 and respectively controlling the energization anddeenergization of relays Z, SP, P, S, and B. The amplifier comparatorcircuit for the energization and deenergization of relay S, includingamplifier A6 is substantially the same configuration as was the casewith respect to the amplifier comparator circuit for the lock out relayL0. The amplifier comparator circuits for the energization of relay Z,SP, P, and B and respectively including amplifier comparators A3, A4, A5and A7 only differ from the amplifier circuits for energization anddeenergization of relays L0 and S in that an additional potentiometer isincluded in each of them, namely, potentiometer POTl, POT2, POT3, andPOT4 respectively through back relay contacts Z3, SP3, P3, and B3respectively. Otherwise resistors R12, R13, R15, R16 and R17,transistors 02 and O8 in the circuit for the energization anddeenergization of relay Z, resistors R19, R20, R22, R23, and R24,transistors 03 and O9 in the circuit for the energization anddeenergization of relay SP, resistors R26, R27, R29, R30, and R31,transistor Q4 and Q10 in the circuit for the energization anddeenergization of relay P, andresistors R40, R41, R43, R44, and R45,transistors 06 and Q12 of the circuit for the energization anddeenergization of relay B all perform the same type functions asresistors R3, R8, R9, R10, and R11, transistors Q1 and Q7 in the circuitfor the energization and deenergization of relay L0, and resistors R33,R34, R36, R37, and R38 and transistors 05 and Q11 in the circuit for theenergization and deenergization of relay S do. Further, diodes 500,501,502, 503,504 and 505 are incorporated in their respective circuits toprovide field shunting to prevent inductive transient voltage spikes andprotected respective transistors associated therewith. Resistors R1 1c,R18, R25, R32, R39 and R46 are incorporated in their respective circuitsto match relay voltages with required polarity.

The potentiometers POTl, POT2, POT3 and POT4 add hysteresis to theirrespective circuits in a predetermined fashion such that thecorresponding relays 2, SP, P, and B will be energized at givenpreselected speed errors (referred to earlier as lower states) wheneverthe vehicle carrying propulsion units 81 and 82 are accelerating, andde'energized at different preselected speed errors whenever the vehicleis decelerating. For example, with reference to energization anddeenergization of relay P, should the train be accelerating towards theset speed, or zero speed error, at a speed error of minus one (-1) mileper hour, or one (1) mile per hour below set speed, the potentiometerPR28 is set such that the output of amplifier A5 will go positivethereby causing the energizaof relay P, back contact P3 of relay Pwillclose thereby adding the value at which potentiometer POT3 is set incombination with that of potentiometer PR28. The combined effect ofpotentiometers PR28 and POT3 will be such that relay P amplifier A5 willproduce no output until a speed error of minus four (-4) miles per houror four (4) miles per hour below set speed when the train isdecelerating is attained. Similarly, with reference to the energizationand deenergizawill not be deenergized, i.e.,

tion of relay Z, should the train be accelerating towards set speed, atthe set speed, or zero speed error, potentiometer P1114 is set such thatthe output of amplifier A3 will go positive thereby causing theenergization of relay Z. Upon energization of relay Z, back contact Z3of relay Z will close thereby adding the value at which thepotentiometer POTl is set in combination with that of potentiometerPR14. The combined effect of potentiometers -PR14 and POTl will be suchthat relay Z will be deenergized at a speed error of minus one (I) mileper hour or one (l)mile per hour below set speed when the train isdecelerating.

Similarly, with reference to the energization and deenergization ofrelay SP, should the train be accelerating towards set speed, at the setspeed, or zero speed error, potentiometer PR21 is set such that theoutput of amplifier A4 will go positive thereby causing theenergizationof relay SP. Upon energization of relay SP, back contact SP3of relay SP will close thereby adding the value at which thepotentiometer POT2 is set in combination with that of potentiometerPR21. The combined effect of potentiometers PR21 and POT2 will be suchthat relay SP will be deenergized at a speed error of minus three (3)miles per hour or three (3) miles per hour below set speed when thetrain is decelerating.

Similarly, with reference to the energization and deenergization ofrelay B, should the train be accelerating and overshoot set speed at aspeed error of 7% mile per hour or /2 mile per hour above set speed,potentiometer P42 is set such that the output of amplifier A7 will gopositive thereby causing the energization of relay B. Upon energizationof relay B, back contact B3 of relay B will close thereby adding thevalue at which potentiometer POT4 is set in combination with that ofpotentiometer PR42. The combined effect of potentiometers PR42 and POT4will be such that relay B will be deenergized at a speed error of milesper hour, or the set speed when the train is decelerating.

With reference to the energization and deenergization of relay S,potentiometer PR3S is set such that the output of amplifier A6 will gopositive at a speed error of minus two (2) miles per hour when the trainis accelerating, and when the train is decelerating will go negative ata velocity error infinitesimally numerically greater than minus two (2)miles per hour.

SYSTEM OPERATION Considering FIGS. and 5a and the systems functionaloperation set forth in FIG. 3, let us assume that a desired velocity forthe train including married vehicles A and B is miles per hour, in orderto better understand the circuitry set forth within the propulsioncontrol logic 95. At this point in the description it is reiterated thatselection ofa 15 mile per hour speed limit is intended only to beillustrative of the function of one embodiment of the invention.Accordingly, the 15 mile per hour button 103 of the train speed commandcontrol unit 100 is pushed, or activated and a circuit is completed todeliver a signal representative of a 15 mile per hour desired speed tothe actual speed versus command speed comparator 102 over lead 101. Itshould be noted at this time that each of the commands for the setspeeds of l0, 15, 20, 25, 30 and 35 miles per hour has respectivelyelectrical connections, not shown, to lead 101 and the actual speedversus command speed comparator 102. Hence, assuming a speed of 15 milesper hour is desired, a signal indicative of the desired speed of 15miles per hour is present on lead 101 and is delivered to actual speedversus command speed comparator 102 along with the signal on lead 99from the train speed tachometer 98 indicative of train velocity which wewill consider to be initially 0 miles per hour. Since the speed of 15miles per hour has been selected and is below arbitrarily selected lockout speed of 17 miles per hour, the signal indicative of the desired 15miles per hour speed on lead 1010 to amplifier A2, the comparatorcircuit for the energization and deenergization of lock out relay LO,will not be enough to overcome the effect of potentiometer PR7 at theother input of amplifier A2, and hence, the output of amplifier A2 willnot go positive and relay LO remains deenergized. The effect, of course,is that back contacts L01 and L02 of relay LO will remain open and theseries-parallel mode of operation for either of married cars A or B willnot be employed due to the fact that no energization path is providedfor the line 170, the energization of which is required forseries-parallel operation. Since, initially the actual train speed iszero, i.e., a speed error of -15 miles per hour or 15 miles per hourbelow set speed is encountered, the output of amplifier A1 of the actualspeed versus command speed comparator 102 will go positive, a signalappearing-on output 111 of amplifier Al indicative of a 15 mile per hourspeed error and a portion of this signal will be tapped from resistor R6to lead 111 and to the velocity error detection network 110. All of thepotentiometers PR14, PR21, PR28, PR35, and PR42 input respectively toamplifiers A3, A4, A5, A6 and A7 are set such that their respectiveamplifiers produce no outputs and relays Z, SP, P, S, and B will not beenergized. Accordingly, back contacts Z1 and Z3 of relay Z,

B1 and B3 of relay B, SP1 and SP3 of relay SP, S1 of relay S and P1 andP3 of relay P will remain open, while front contacts Z2 of relay 2, B2of relay B, SP2 of relay SP, P2 of relay P, and S2 of relay S willremain closed. With these contacts in their respective positions at thespeed error of -15 miles per hour, referring to married-pair performancecurve selection logic 80, a circuit will be completed from third rail 86over contact 87, lead 88, lead 151, front contact 22 of relay Z, frontcontact B2 of relay B, lead 156, front contact SP2 of relaySP, lead 160,lead 169, front contact P2 of relay P, lead 188, diode 201, diode 204,to line 172 thereby energizing line 172. A circuit will also becompleted from third rail 86 over contact 87, lead 88, lead 151, frontcontact Z2 of relay Z, front contact B2 of relay B, lead 156, frontcontact SP2 of relay SP, lead 160, lead 169, front contact P2 of relayP, lead 188, diode 201, diode 204, diode 207, to line 173 therebyenergizing line 173. Hence, with lines 172 and 173 energized propulsionunit 81 of car A is placed into its series mode of operation. A circuitis also completed from third rail 86 over contact 87, lead 88, lead 151,front contact Z2 of relay Z,

front contact B2 of relay B, lead 156, front contact SP2 of relay SP,lead 160, lead 169, front contact P2 of relay P, lead 188, lead 190,diode 202, to line 167 thereby energizing line 167 and accordinglyenergizing the X relay of propelling effort control means 91 causingcontacts a, b, and c of the X" relay to close and allow lines 172 and173 to place propulsion unit 82 of car B in its series mode ofoperation, line not being energized. Since both propulsion units 81 and82, cars A and B respectively are in their series modes of operationthey provide a combined tractive effort which is reflected by the trainpropulsion and performance curve 12 of FIG. 3.

A study of FIG. 3 will reveal that once the cars A and B of the marriedpair are commanded into their series modes of operation, the automaticnature of the existing married pair of propulsion units or motors comesinto effect and the train initially will attempt to follow theperformance curve 11, which is the switching curve. A CHANGE IN VELOCITYWILL AUTOMATICALLY CAUSE THE INCREMENTAL ADDI- TION OR SUBTRACT ION OFRESISTANCES TO THE WINDINGS OF THE PROPULSION UNITS 81 and 82 to allow,as has been described earlier, the married-pair to move along at amaximum acceleration rate up to the curve 12.

Therefore, the train will continue to accelerate as the tractive effortpresented by the married-pair performance curve 12 is greater than thetrain resistance as illustrated by the train resistance curve 17. Thetrains velocity accordingly, will increase toward the set speed of 15miles per hour and follow the curve 12 downwardly to the point 760 onthe curve 12, which is at a speed error of minus two (2) miles per hourand decreasing numerically. The potentiometer PR35, input to amplifierA6 in the circuit for the energization and deenergization of relay S invelocity error detection network 110, is set such that the output ofamplifier A6 will go positive at a velocity error of minus two (-2)miles per hour when the train is accelerating and relay S will beenergized thereby closing back contact S1 of relay S and opening frontcontact S2 of relay S. Due to potentiometer PR35 relay S will remainenergized until a speed error infinitesimally numerically greater thanminus two (-2) miles per hour is encountered when the train isdecelerating. However, since back contact SP1 of relay SP remains open,there will be no effective change in train performance and the trainwill continue along curve 12 until it reaches point 61 on curve 12. Whenthe point 61 on curve 12 is reached at the arbitrarily selected velocityerror of minus one (1) mile per hour, the potentiometer PR28 input toamplifier A in the circuit for the energization and deenergization ofrelay P, is set such that the output of amplifier A5 will go positivethereby causing the energization of relay P and accordingly, the closingof back contacts P1 and P3 of relay P and the opening of front contactP2 of relay P. The closing of back contact P3 now allows the combiningof potentiometers POT3 and PRZS to add-hysteresis to the circuit forenergization and deenergization of relay P, the effect being that relayP will not deenergize until a velocity error of minus four (-4) milesper hour is reached when the train decelerates. The closing of backcontact P1 of relay P and opening of front contact P2 of relay P causesa change in energization paths in the married pair performance curveselection logic 80. A path for the energization of line 172 is stillmaintained from third rail 86 over contact 87, lead 88, lead 151, frontcontact Z2 of relay Z, front contact B2 of relay B, lead 156, frontcontact SP2 of relay SP, lead 160, lead 166, back contact P1 of relay P,lead 187, diode 204, to line 172. A path for the energization of line173 is also still maintained from third rail 86 over contact 87, lead88, lead 151, front contact Z2 of relay Z, front contact B2 of relay B,lead 156, back contact SP2 of relay SP, lead 160, lead 166, back contactP1 of relay P, lead 187, diode 204,

- diode 207, to lead 173. Hence, since lines 172 and 173 remainenergized, propulsion unit 81 of car A remains in its series mode ofoperation via leads 172a and 173a. However, because of the opening offrom contact P2 of relay P, and the direction of diode 201, power toline 167 will now be cut off thereby causing the deenergization of the Xrelay of the propelling effort control means 91 and the opening ofcontacts a, b, and c of the X relay. Hence, with the opening of contactsa, b, and c of the X relay, no power whatsoever reaches propulsion unit82 of car B and car B is now in its coast mode of operation. With car Ain its series mode of operation and car B in its coast mode ofoperation, the tractive effort of the married pair of cars is decreasedby approximately one-half so that the train will begin to follow marriedpair performance curve 32 at point 61a which indicates a minus one (-1)mile per hour velocity error.

The train now continues to accelerate to the zero velocity error, or setspeed, corresponding to a point 62 on married pair performance curve 32.This, of course, presumes that the tractive effort afforded by the curve32 exceeds the train resistance'which is'represented by the family ofcurves 17, 17a, and 17b. It should be kept in mind that the curves 17,17a and 17b are dynamically fluctuating in their movement as grade andwind force act upon the train.

For purposes of illustration only the description that will ensue willassume for a brief moment that at this point in the description theinertia of the train will approach set speed at a lower rate, but thatset speed will be reached. Accordingly, when zero velocity error isattained, the potentiometer PR14 input to amplifier A3 of the comparatorcircuit for the energization and deenergization of relay Z, is set suchthat at zero velocity error the output amplifier A3 will go positivethereby causing the energization of the relay Z and the closing of backcontacts Z1 and Z3 of relay Z and the opening of front contact Z2 ofrelay Z. Also at zero velocity error, potentiometer PR21 input toamplifier A4 of the comparator circuit for the energization anddeenergization of relay SP, is set such that the output of amplifier A4will go positive thereby causing the energization of relay SP and theclosing of back contacts SP1 and SP3 of relay SP and the opening offront contact SP2 of relay SP. The closing of back contact Z3 of relay Zcombines potentiometer POT1 with potentiometer PRM as an input toamplifier A3 thereby adding hysteresis to the circuit for theenergization and deenergization of relay Z. The effect of this addedhysteresis will be such that relay Z will not be deenergized until aspeed error of minus one (-1) mile per hour is reached when the train isdecelerating. Similarly, the closing of back contact SP3 of relay SPcombines potentiometer POT2 with potentiometer PR21 as an input toamplifier A4 thereby adding hysteresis to the circuit for theenergization and deenergization of relay SP. The effect of this addedhysteresis will be such that relay SP willnot be deenergized until aspeed error of minus three (-3) miles per hour is attained when thetrain is decelerating. The closing of back contact Z1 of relay Z andopening of front contact Z2 of relay Z at zero speed error when thetrain is accelerating now causes an open circuit with respect to powerentering married-pair performance curve selection logic since backcontact B1 of relay B remains open and now front contact Z2 of relay Zis open. Hence, none of the lines 167, 170, 172, or 173 will beenergized and both propulsion units 81 and 82 of cars A and B,respectively, will be in their coast modes of operation. With both carsA and B in their coast modes of operation, a dynamic braking effect willoccur as well as decelerating effects due to train inertia. The trainwill now begin to follow the dynamic braking curve 16 at point 64. Thisdynamic braking curve 16 has been described in detail with reference toFIG. 3 and no further explanation will be entertained at this point inthe description. Should the train continue to accelerate, for example,due to a sudden down grade, an overspeed braking will occur at avelocity error of mile per our, or 1% mile per hour above set speed. Ifthis /2 mile per hour velocity error is attained, the potentiometerPR42, input to amplifier A7 of the circuit for the energization anddeenergization of relay B, is set such that at /2 mile per hour velocityerror the output of amplifier A7 will go positive thereby causing theenergization of relay B and the closing of back contacts B1 and B3 ofrelay B and the opening of front contact B2 of relay B. The closing ofback contact B3 of relay B combines potentiometer POT4 withpotentiometer PR42 as an input to amplifier A7 thereby adding hysteresisto the circuit for the energization and deenergization of relay B. Theeffect of this added hysteresis will be such that relay B will not bedeenergized until a zero speed error, or set speed, is attained when thetrain is decelerating. The opening of front contact B2 maintains theopen circuit condition with respect to energization paths within themarried pair performance curve selection logic 80 such that neither carA or B receives signals from the marriedpair performance curve selectionlogic 80. Keeping in mind that back contact Z1 of relay Z is stillclosed, the closing of back contact B1 of relay B completes a circuitfrom third rail 86 over contact 87, lead 88, lead 150, back contact Z1of relay Z, back contact B1 of relay B, lead to a braking relay locatedon car A, thereby energizing the brake control circuit and causing amechanical braking to prevent further overspeed of the train.

By the application of actual train brakes coupled with the ever presentinherent dynamic braking when both cars A and B are in coast, the trainbegins deceleration along the curve 16 until it reaches, once again, thezero velocity error, or set speed indicated at point 65 on curve 16.Since, upon deceleration the train has once again reached zero velocityerror, or set speed, relay B, as previously described, will now becomedeenergized thereby causing the opening of back contacts B1 and B3 ofrelay B and the closing of front contact B2 of relay B. The opening ofback contact B1 of relay B will cause relay B to be deenergized therebyreleasing the mechanical train brakes. Because contact Z2 of relay Zremains open, no paths of energization for lines 167, 170, 172, or 173out of marriedpair performance curve selection logic 80 are present.Hence cars A and B are both in their coast modes of operation, the trainnow following dynamic braking curve 16 at point 64 which represents zerovelocity error.

higher total tractive effort. Accordingly, at a velocity error of minusone (1) mile per hour, represented by point 65 on curve 16, relay Z willbe deenergized due to the previously described added hysteresis to thecircuit for the energization and deenergization of relay Z. Hence, backcontacts Z1 and Z3 of relay Z will be opened and front contact Z2 ofrelay Z will be closed. Recalling that relays SP and S are stillenergized, an energization path will be completed from third rail 86over contact 87, lead 88, lead 151, front contact Z2 of relay Z, frontcontact B2 of relay B, lead 154, back contact SP1 of relay SP, lead 158,lead 163, back contact S1 of relay S, lead 180, to line 173 therebyenergizing line 173. Line 172 will not be energized because frontcontact SP2 of relay SP is open, back contact L01 of relay L is open,and also because of the direction of the diodes 200 and 207. Nor willline 167 be energized because front contact SP2 of relay S is open andbecause of the direction of diode 200. Hence, with line 173 being theonly line to be energized, propulsion unit 81 of car A will be placed inits switch mode of operation via lead 1730. Since line 167 is notenergized, the X relay of propelling effort control means 91 remainsdeenergized, and contacts a, b, and c of the X relay remain open.Accordingly, propulsion unit 82 of car B will remain in its coast modeof operation. Hence, with car A in its switch mode of operation and carB in its coast mode of operation, the train will now follow marriedpairperformance curve 31, beginning at the point 66, which is located abovethe 14 mile per hour velocity shown in FIG. 3.

Should the train continue to decelerate, it will follow married-pairperformance curve 31 until it reaches a point 67, directly above the 13mile per hour velocity indication, or at a velocity error of minus two(2) miles per hour. Accordingly, at a velocity error infinitesimally tothe left of minus two (-2) miles per hour, relay S will be deenergizeddue to the effect of potentiometer PR35 on the circuit for theenergization and deenergization of relay S, as previously described.Hence, back contact S1 of relay S will be opened, and front contact S2of relay S will be closed. Recalling that relay SP is still energized,an energization path will be completed from third rail 86 over contact87, lead 88, lead 151, front contact Z2 of relay Z, front contact B2 ofrelay B, lead 154, back contact SP1 of relay SP, lead 158, lead 165,front contact S2 of relay S, lead 181, diode 200, lead 182, to line 173,thereby maintaining line 173 in an energized state. Line 172 will not beenergized because back contact L01 of relay L0 is open and because ofthe direction of diode 207. However, an energization path for line 167is provided from third rail 86 over contact 87, lead 88, lead 151, frontcontact Z2 of relay Z, front contact B2 of relay B, lead 154, backcontact SP1 of relay SP, lead 158, lead 165, front contact S2 of relayS, lead 181, lead 184, to line 167. Since line 173 and not line 172 isenergized, propulsion unit 81 of car A will continue to operate in itsswitch mode of operation via lead 173a. Further, because line 167 isonce again energized, the X relay of propelling effort control means 91will be energized thereby causing contacts a, b, and c of the X" relayto close, and with line 173 being the only other line to be energized,propulsion unit 82 of car B will be placed in its switch mode ofoperation via lead 1730. Both cars A and B being in their switch modesof operation, the train follows the next higher married-pair tractiveeffort curve, namely, married-pair performance curve 11, beginning atpoint 68 thereon in FIG. 3.

Should the train decelerate further, it will follow marriedpairperformance curve 11 until a velocity error of minus three (3) miles perhour is reached as indicated by point 69 i on curve 11. Accordingly, atan error infinitesimally numerically greater than minus three (3) milesper hour, the previously described added hysteresis of potentiometerPOT2 to the circuit for the energization and deenergization of relay SFwill cause the deenergization of relay SP as previously noted. Hence,back contacts SP1 and SP3 of relay SP will be opened, while frontcontact SP2 of relay SP will be closed. With the closing of frontcontact SP2 of relay SP, recalling that relay P third rail 86 overcontact 87, lead 88, lead 151, front contact Z2 of relay Z, frontcontact B2 of relay B, lead 156, front contact SP2 of relay SP, lead160, lead 166, back contact P1 of relay P, lead 187, diode 204, to line172 thereby energizing line 172. A circuit is also completed fromthird'rail 86 over contact 87, lead 88, lead 151, front contact Z2 ofrelay Z, front contact B2 of relay 13, lead 156, front contact SP2 ofrelay SP, lead 160, lead 166, back contact P1 of relay P, lead 187,diode 204, diode 207, to line 173 thereby energizing line 173. No pathof energization is provided for line 167 because of open front contactP2 of relay P and also because of the direction of diode 201 and,therefore, line 167 will be deenergized. With the deenergization of line167, the X relay of the propelling effort control means 91 will bedeenergized causing contacts a, b, and c of the X relay to be opened.Hence, with energization of both lines 172 and 173, propulsion unit 81of car A will be placed in its series mode of operation via leads 172aand 173a respectively. However, since contacts a, b, and c of the X"relay are opened, no power will reach propulsion unit 82 of car B andthat unit will be placed in its coast mode of operation. Due to a highertractive effort afforded by car A being in its series mode of operationand car B in its coast mode of operation, the train will now begin tofollow married-pair performance curve 32 at the point 70 in FIG. 3.

It should be kept in mind that at any pointalong any particularmarried-pair performance curve, which the train is following, should thetrain be above the train resistance curve 17, as is point 70 onmarried-pair performance curve 32, the train will once again beginaccelerating in accordance with the particular married-pair performancecurve until it reaches a point where it may follow a lower married-pairperformance curve due to a lower tractive effort requirement. But forpurposes of illustration, let us assume that such an occurrence does nothappen. In order to trace the remaining circuits, it will be presumedthat the train resistance is greater than the tractive effort beingsupplied.

Accordingly, should the train further decelerate, it will follow alongmarried pair performance curve 32, beginning from point 70, to a point71, directly above the minus four (4) miles per hour. velocity errorindication in FIG. 3. Accordingly, at an error infinitesimallynumerically greater than minus four (4) miles per hour, the previouslydescribed added hysteresis of potentiometer POT3 to the circuit for theenergization and deenergization of relay P will cause the deenergizationof relay P as previously noted. Hence, back contacts P1 and P3 of relayP will be opened, while front contact P2 of relay P will be closed. Withthe closing of front contact P2 of relay P, and keeping in mind that atthis point none of the relays LO, Z, SP, P, S, or B is energized, anenergization path will be completed from third rail 86 over contact 87,lead 88, lead 151, front contact Z2 of relay Z, front contact B2 ofrelay B, lead 156, front contact SP2 of relay SP, lead 160, lead 169,front contact P2 of relay P, lead 188, diode 201, diode 204, to line 172thereby energizing line 172. Ah energization path will also be completedfrom third rail 86 over contact 87, lead 88, lead 151, front contact Z2of relay Z, front contact B2 of relay B, lead 156, from contact SP2 ofrelay SP, lead 160, lead 169, front contact P2 of relay P, lead 188,diode 201, diode 204, diode 207 to line 173 thereby energizing line 173.An energization path is also provided from third rail 86 over contact87, lead 88, lead 151, front contact Z2 of relay Z, front contact B2 ofrelay B, lead 156, front contact SP2 of relay SP, lead 160, lead 169,front contact P2 of relay P, lead 188, lead 190, diode 202, to line 167thereby energizing line 167. With lines 172 and 173 energized,propulsion unit 81 of car A will be maintained in its series mode ofoperation via leads'172a and 173a. Further, with line 167 energized theX" relay of propelling effort control means 91 will be energized therebycausing contacts a, b, and c of the X relay to be closed and allowingpower from the lines 172 and 173 to reach propulsion unit 82 of car Bvia leads 1720 and 1730, respecis still energized, an energization pathwill be completed from tively. Accordingly, propulsion unit 82 of car Bwill be placed in its series mode of operation. With car A in itsseriesmode of operation and car B being placed in its series mode ofoperation from its coast mode of operation, a higher overall marriedpair tractive effort will be produced. Accordingly, the train will nowfollow the married-pair performance curve 12 beginning at point 76. Itwill be seen that the entire speed control process just recited will nowrecycle.

It will be appreciated that while the specific married-pair vehicularoperation shown and disclosed is directed to only a portion of thefamily of married-pair performance curves, shown in the aforementionedpreferred embodiment of the invention in FIG. 2, that portionillustrated in FIG. 3, the underlying inventive concept extends itselfto the entire family of curves associated with the preferred embodiment,although not shown herein.

From the foregoing teachings it is apparent that, while the invention isdescribed in a preferred embodiment of a mar ried-pair train propulsionsystem, there are other areas where the, teachings are equallyapplicable. For example, where there is a pair or pairs of motorsavailable to drive a given variable load and each of the motors has morethan one mode or operating state, then married pair motor control logicmay be employed in conjunction with a load driving control X relay toprovide smoother control over the variable load.

In addition, the teachings of the invention will find equally applicableuse in married-pair propulsion systems of the future where thetechnology is advancing with reference to the use of solid statedevices. It is becoming increasingly apparent that propulsion systemswill not experience a sudden metamorphosis to produce total changeoverto solid state control of propulsion motors. The change will be one ofevolution wherein more solid state devices will be employed in thesystem control, but this will not obviate the basic economics which callfor the continued use of many of the proven control techniques. It is tothis evolution that the current teachings provide the economic salve toease the change.

While the invention has been shown and depicted with reference to apreferred embodiment thereof, it will be understood by those skilled inthe art that other embodiments may be made therein without departingfrom the spirit and scope of the invention.

Having thus described my invention, what i claim is:

l. A multiple vehicle propulsion control system for causing vehicularmovement along a predetermined path at a preselected speed relativelyfree from accelerating and decelerating effects, said system comprising:

a. a separate propulsion unit on each vehicle, each vehicle propulsionunit having a plurality of distinct selectable operating modes inaddition to a braking mode, one of said propulsion units being a primarypropulsion unit, another of said propulsion units on another vehiclebeing a secondary propulsion unit,

b. propelling effort control means having a first and a second statedetermined in accordance with the propelling effort required to maintainsaid preselected vehicular speed relatively free from accelerating anddecelerating effects and operatively coupled to said secondarypropulsion unit,

c. vehicle-carried propulsion control logic means controllingly coupleddirectly to said primary propulsion unit and indirectly to saidsecondary propulsion unit through said propelling effort control means,said vehicle-carried propulsion control logic means including,

1. vehicular speed command control means,

2. vehicular speed measuring means,

3. speed comparator means, said speed comparator means coupledrespectively to said vehicular speed command control means and saidvehicular speed measuring means to thereby provide an output indicativeof vehicular velocity change,

'4. velocity error detecting means coupled to said speed comparatormeans and controlled by said speed comparator means output to provide anerror si na l output,

5. propulsion unit operating mode selection logic means which ismutually coupled to a power supply and said velocity error detectingmeans and is controlled by said velocity error detecting means errorsignal output,

a. said propulsion unit operating mode selection logic means having anoutput to select a particular set of one of said plurality of operatingmodes in addition to said braking mode for said primary and secondarypropulsion unit and directly actuating said particular operating mode insaid primary propulsion unit, said secondary propulsion unit beingactuated into said particular operating mode only when said propellingeffort control means is in said second state,

b. said secondary propulsion unit operating at a predetermined referenceoperating mode when said propelling effort control means is in saidfirst state.

2. The vehicular control system of claim 1 wherein said propulsion unitsare electric motors.

3. The vehicular control system of claim 2 wherein said electric motorsare do. series-connected motors.

4. The vehicular control system of claim 3 wherein said plurality ofoperating modes are equivalent to series-connected electric motorperformance curves.

5. The vehicular control system of claim 4 wherein said preselectedreference operating mode corresponds to a coasting electric motorperformance curve.

6. The vehicular control system of claim 1 wherein each of saidpropulsion units has an equal number of propulsion modes of similarpropulsion effort.

7. The vehicular control system of claim 1 wherein each of saidpropulsion units is positioned on a separate vehicle.

8. The vehicular control system of claim 1 wherein said propellingeffort control means is an electromagnetic device.

9. The. vehicular control system of claim 8 wherein said electromagneticdevice is a relay with multiple contacts.

1. A multiple vehicle propulsion control system for causing vehicularmovement along a predetermined path at a preselected speed relativelyfree from accelerating and decelerating effects, said system comprising:a. a separate propulsion unit on each vehicle, each vehicle propulsionunit having a plurality of distinct selectable operating modes inaddition to a braking mode, one of said propulsion units being a primarypropulsion unit, another of said propulsion units on another vehiclebeing a secondary propulsion unit, b. propelling effort control meanshaving a first and a second state determined in accordance with thepropelling effort required to maintain said preselected vehicular speedrelatively free from accelerating and decelerating effects andoperatively coupled to said secondary propulsion unit, c.vehicle-carried propulsion control logic means controllingly coupleddirectly to said primary propulsion unit and indirectly to saidsecondary propulsion unit through said propelling effort control means,said vehicle-carried propulsion control logic means including, 1.vehicular speed command control means,
 2. vehicular speed measuringmeans,
 3. speed comparator means, said speed comparator means coupledrespectively to said vehicular speed command control means and saidvehicular speed measuring means to thereby provide an output indicativeof vehicular velocity change,
 4. velocity error detecting means coupledto said speed comparator means and controlled by said speed comparatormeans output to provide an error signal output,
 5. propulsion unitoperating mode selection logic means which is mutually coupled to apower supply and said velocity error detecting means and is controlledby said velocity error detecting means error signal output, a. saidpropulsion unit operating mode selection logic means having an output toselect a particular set of one of said plurality of operating modes inaddition tO said braking mode for said primary and secondary propulsionunit and directly actuating said particular operating mode in saidprimary propulsion unit, said secondary propulsion unit being actuatedinto said particular operating mode only when said propelling effortcontrol means is in said second state, b. said secondary propulsion unitoperating at a predetermined reference operating mode when saidpropelling effort control means is in said first state.
 2. vehicularspeed measuring means,
 2. The vehicular control system of claim 1wherein said propulsion units are electric motors.
 3. The vehicularcontrol system of claim 2 wherein said electric motors are d.c.series-connected motors.
 3. speed comparator means, said speedcomparator means coupled respectively to said vehicular speed commandcontrol means and said vehicular speed measuring means to therebyprovide an output indicative of vehicular velocity change,
 4. velocityerror detecting means coupled to said speed comparator means andcontrolled by said speed comparator means output to provide an errorsignal output,
 4. The vehicular control system of claim 3 wherein saidplurality of operating modes are equivalent to series-connected electricmotor performance curves.
 5. The vehicular control system of claim 4wherein said preselected reference operating mode corresponds to acoasting electric motor performance curve.
 5. propulsion unit operatingmode selection logic means which is mutually coupled to a power supplyand said velocity error detecting means and is controlled by saidvelocity error detecting means error signal output, a. said propulsionunit operating mode selection logic means having an output to select aparticular set of one of said plurality of operating modes in additiontO said braking mode for said primary and secondary propulsion unit anddirectly actuating said particular operating mode in said primarypropulsion unit, said secondary propulsion unit being actuated into saidparticular operating mode only when said propelling effort control meansis in said second state, b. said secondary propulsion unit operating ata predetermined reference operating mode when said propelling effortcontrol means is in said first state.
 6. The vehicular control system ofclaim 1 wherein each of said propulsion units has an equal number ofpropulsion modes of similar propulsion effort.
 7. The vehicular controlsystem of claim 1 wherein each of said propulsion units is positioned ona separate vehicle.
 8. The vehicular control system of claim 1 whereinsaid propelling effort control means is an electromagnetic device. 9.The vehicular control system of claim 8 wherein said electromagneticdevice is a relay with multiple contacts.